1. Field of the Invention
The present invention relates to a high-density information recording technique using a focused beam (blue laser or the like). More particularly, the present invention relates to an improvement in an information recording method for a high-density optical disc on/from which digital information is recorded/reproduced at constant linear velocity (CLV). Also, the present invention relates to an inter-layer crosstalk reduction technique in a recordable optical disc having a recording multilayer including two or more layers per side.
2. Description of the Related Art
As a high-density information storage capable of repeated recording (repeated rewrite) using a focused beam, optical discs such as a DVD-RAM, DVD-RW, and the like is known.
<<Problem 1>>
In a DVD-RW (rewritable medium), new data is recorded by partially overwriting an already data recorded portion (Restricted Overwrite). In this case, since already recorded data is partially destroyed to record the next data, the reliability of information recorded on an information storage medium suffers considerably.
<<Problem 2>>
On the other hand, a DVD-RAM (repeated recordable medium) suffers the following problems:
a) Since data are recorded between neighboring ones of a large number of prepit headers present on an information storage medium, the information recording efficiency (recording density) lowers, thus disturbing large capacity.                b) When a two-recording layer structure per side is adopted for large capacity, inter-layer crosstalk is generated due to prepit headers, thus deteriorating reproduction signal characteristics. That is, in a recording layer, since recorded and unrecorded portions have a light reflectance difference, inter-layer crosstalk in which the presence/absence of recording marks on the other recording layer influences a reproduction signal is generated, thus deteriorating reproduction signal characteristics.        